RFR (L): 8076454, 8076289 and 8076452: removing SharedHeap

[Bengt Rutisson]

Hi everyone,

Could I have a couple of reviews for these three patches to remove 
SharedHeap?

I'm sending all three patches in the same email because I think they are 
closely related. But I am planning to push them at three separate changes.

JDK-8076454: Clean up/move things out of SharedHeap
https://bugs.openjdk.java.net/browse/JDK-8076454
http://cr.openjdk.java.net/~brutisso/8076454/webrev.00/


JDK-8076289: Move the StrongRootsScope out of SharedHeap
https://bugs.openjdk.java.net/browse/JDK-8076289
http://cr.openjdk.java.net/~brutisso/8076289/webrev.00/


JDK-8076452: Remove SharedHeap
https://bugs.openjdk.java.net/browse/JDK-8076452
http://cr.openjdk.java.net/~brutisso/8076452/webrev.00/



Some more details about the changes:

JDK-8076454 contains many small changes. Here's the steps I took to 
complete the patch. It may be easier to review each step of the way:

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_gcprologue/
This removes the pure virtual implementations of 
SharedHeap::gc_prologue() and SharedHeap::gc_epilogue() since there are 
no callers of these methods. All calls are directly to the concrete 
subclasses.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_set_barrier_set/
This removes SharedHeap::set_barrier() and instead inlines the code in 
G1CollectedHeap and GenCollectedHeap similarly to what 
ParallelScavengeHeap already does.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-move_post_initialized_and_ref_init/
SharedHeap::post_initialize() was just forwarding to 
CollectedHeap::post_initialize() and adding a call to 
ref_processing_init(). Moved this down to the concrete sub classes.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_no_gc_in_progress/
no_gc_in_progress() is only used in GenCollectedHeap so it is enough 
that it is declared there.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_space_iterate/
space_iterate() was dead code.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_oop_iterate/
oop_iterate() is already declared pure virtual in CollectedHeap, so no 
need to have it in SharedHeap too.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_space_containing/
There were no callers of SharedHeap::space_containing(). No need to have 
a virtual method in SharedHeap. Enough to declare the methods in the 
concrete sub classes.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-cleanup_includes_and_friends/
Just some cleanups of includes and friend declarations. Not really 
relevant as the file will be completely removed by JDK-8076452.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_set_par_threads/
SharedHeap::set_par_threads() only introduced an assert compared to what 
CollectedHeap::set_par_threads() already does. The assert is only 
relevant in the GenCollectedHeap case. So I moved the assert down to 
that class.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-move_workers/
Move the instance variable to hold the FlexibleWorkGang (_workers) down 
to the concrete sub classes. Only two lines of common code, so hardly 
worth sharing.

http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-product-fix/
I had a mistake for product builds regarding set_heap_lock_held_for_gc().



JDK-8076289 moves the StrongRootsScope class out to its own file.

http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-remove_StrongRootsScope_sh/
The StrongRootsScope no longer makes use of its SharedHeap instance 
variable, so it can be removed and the constructor does not have to take 
it as a parameter.

http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_StrongRootsScope/
Move the StrongRootsScope out to its own files and to the global name space.

http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_MarkScope/
Move the super class of StrongRootsScope, MarkScope, into the same files.

I would like to follow this change up with a couple of things. I would 
like to rename StrongRootsScope to something like RootProcessingScope 
since we no longer use it purely for strong roots. I would like to 
rename MarkScope to something like NMethodScope. And I think 
ParallelScavenge could use MarkScope directly instead of introducing 
ParStrongRootsScope. But I would like to do these changes as a separate 
patch.


JDK-8076452 is pretty much just one patch to get rid of all reference to 
SharedHeap now that it is empty after the above changes.

Thanks,
Bengt